Capacitor for a semiconductor device

ABSTRACT

In a method for forming a photoresist pattern, a method for forming a capacitor, and a capacitor manufactured using the same, a light is selectively irradiated onto a selected portion of a photoresist film formed on a substrate. An interfered light generated from the irradiated light is transmitted through other portions of the photoresist film except a ring-shaped portion of the photoresist film having a predetermined width along a boundary of the selected portion. The photoresist film is exposed using the interfered light and the light irradiated onto the selected portion. A cylindrical photoresist pattern having a minute width may be formed through developing the photoresist film. With the cylindrical pattern, the capacitor can be easily formed.

CROSS REFERENCE TO RELATED APPLICATION

This is a divisional application based on application Ser. No.10/459,593, filed Jun. 12, 2003 now U.S. Pat. No. 7,135,272, the entirecontents of which is hereby incorporated by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a method for forming a photoresistpattern, a method for forming a capacitor electrode using the same and acapacitor. More particularly, the present invention relates to a methodfor forming a ring-type photoresist pattern having an open bottom faceand an open upper face, a method for forming a capacitor using the same,and a capacitor manufactured by using the ring-type photoresist pattern.

2. Description of the Related Art

For functionality, semiconductor devices require fast operation and highaccumulation capacity. For this purpose, manufacturing technologies forimproving integration density, response speed and reliability are beingdeveloped.

Dynamic random access memory (DRAM) is widely used as a semiconductordevice that can input and output information. A DRAM has a cell regionfor storing information data in the form of electrons and a peripheralcircuit region for transferring information data to or from the cellregion. A DRAM device typically includes one access transistor and onestorage capacitor.

As the degree of integration of semiconductor devices increases, itbecomes difficult to improve the capability of a capacitor because thehorizontal area that the capacitor occupies decreases. To increase thestorage capability of a capacitor, a method for increasing an efficientarea of the capacitor has been developed. According to the method, thestructure of a capacitor is varied from a planar structure to a stackedstructure or a trench-type structure. A stacked capacitor may be furthervaried to have a cylindrical structure to increase the effective area ofthe storage electrode.

Other structures for increasing the capacitance of a capacitor include astacked capacitor having a crown shape, a stacked capacitor having a pinshape, and a capacitor having hemispherical silicon grains formed on astorage electrode thereof.

However, according to conventional methods for forming capacitors,additional processes may be necessary to vary the structure of acapacitor, thereby complicating the method for manufacturing thecapacitor.

To grow the hemispherical silicon grains on the storage electrode of thecapacitor mentioned above, a sufficient interval between storageelectrodes is necessary to prevent a bridge between the storageelectrodes. However, to realize a more highly integrated semiconductordevice, a design rule thereof has been reduced, and an interval betweenstorage electrodes of the semiconductor device has become even moreminiscule. As a result, there may be a limit for growing hemisphericalsilicon grains on storage electrodes.

FIGS. 1A to 1D illustrate cross sectional views depicting a conventionalmethod for forming a cylindrical capacitor.

Referring to FIG. 1A, a first insulation film 12 is formed on asemiconductor substrate 10, and a contact plug 14 making contact withthe semiconductor substrate 10 is formed at a predetermined portion ofthe first insulation film 12.

An etch stop film 16 is formed on the first insulation film 12, and asecond insulation film 18 is formed on the etch stop film 16.

Referring to FIG. 1B, an opening 20 exposing an upper portion of thecontact plug 14 and a portion of the first insulation film 12 is formedby successively etching predetermined portions of the second insulationfilm 18 and the etch stop film 16 to make a second insulation filmpattern 18 a and an etch stop film pattern 16 a.

A polysilicon film having a uniform thickness is formed on a sidewalland a bottom face of the opening 20, and on an upper face of the secondinsulation film pattern 18 a. A sacrificial layer (not shown) is formedon the polysilicon film to fill the opening 20 having the polysiliconfilm formed thereon, and an upper portion of the sacrificial layer isplanarized by an etch back process to separate the polysilicon film intoa storage node. The sacrificial layer is removed to form storage nodeelectrode 22, as shown in FIG. 1C.

Referring to FIG. 1D, a capacitor is completed by forming a dielectricfilm 24 and a plate electrode 26 on the storage node electrode 22.

In the method described above for manufacturing a cylindrical capacitor,complicated manufacturing processes including a deposition process forthe insulation films, an etching process, a deposition process for thepolysilicon film, a deposition process for the sacrificial layer, and aseparation process for the storage node are performed to form thecylindrical storage node electrode node. Therefore, processing failuresmay occur during any of the complicated processes, and a productivity ofthe capacitor may be reduced.

In an attempt to solve the problems mentioned above, a method forforming a semiconductor device using a phase shift mask has beenproposed. However, according to the method, the height of a storage nodeelectrode may not be increased because the low structure of the storagenode electrode may be unstable. In addition, with the phase shift mask,the phase of light passing through a phase inversion material of thephase shift mask may not be inverted so that the light passing throughthe phase inversion material has an intensity identical to that of lightpassing through an open region of the phase shift mask.

SUMMARY OF THE INVENTION

In an effort to solve the problems described above, it is a feature ofan embodiment of the present invention to provide a method for forming acylindrical type photoresist pattern having an open upper face and anopen bottom face.

It is a second feature of an embodiment of the present invention toprovide a capacitor having a cylindrical storage node electrode.

It is a third feature of an embodiment of the present invention toprovide a simplified method for forming an electrode of a capacitorelectrode.

In one aspect, according to a method for forming a photoresist patternof one preferred embodiment of the present invention, a photoresist filmis exposed by selectively irradiating a selected portion of thephotoresist film formed on a semiconductor substrate with light, whereina portion of the light that undergoes interference is irradiated onto aportion of the photoresist film other than the selected portion of thephotoresist film and a portion of the photoresist film having apredetermined width that borders the selected portion, so that thephotoresist film is exposed by both the light irradiated onto theselected portion and the portion of the light that undergoesinterference. Then, the exposed photoresist film is developed to form acylindrical photoresist pattern.

The photoresist film may be exposed by the light irradiated onto theselected portion and a transmitting light irradiated onto the portion ofthe photoresist film other than the selected portion and the portionbordering the selected portion, the transmitting light having a phasethat is the inverse of a phase of the light irradiated onto the selectedportion.

An intensity of a transmitting light irradiated onto the portion of thephotoresist film other than the selected portion and the portionbordering the selected portion is preferably about 5% to about 50% thatof the light irradiated onto the selected portion.

The selected portion may include regularly disposed regions of thephotoresist film. A first interfered light generated from the lightirradiated onto a first selected portion is superposed with interferedlights generated from the light irradiated onto the selected portionsadjacent to the first selected portion to increase an intensity of thelight exposing the photoresist film.

A width of a ring-shaped portion generated along the border of theselected portion may be adjusted in accordance with the intensity of thelight irradiated onto the selected portion.

Because the photoresist film is exposed using the light irradiated ontothe selected portion and the interfered light, a cylindrical photoresistpattern having a minute width can be formed.

According to another feature of an embodiment of the present invention,a capacitor is provided including an insulation film having a contactplug formed on a semiconductor substrate, a cylindrical storage nodeelectrode formed on the insulation film, wherein the storage nodeelectrode makes electrical contact with the contact plug and has an openbottom face, and a dielectric film and a plate electrode successivelyformed on the storage node electrode. Preferably, a portion of thebottom face of the storage node electrode makes contact with an upperface of the contact plug.

In an effort to provide the second feature of an embodiment of thepresent invention, a capacitor is provided including an insulation filmincluding a contact plug formed on a semiconductor substrate, aring-shaped pad polysilicon film pattern electrically connected to thecontact plug, a double cylindrical storage node electrode in continuouscontact with inner and outer surfaces of the ring-shaped pad polysiliconfilm pattern, wherein the storage node electrode extends vertically fromthe inner and outer surfaces of the ring-shaped pad polysilicon filmpattern and a dielectric film and a plate electrode formed on thestorage node electrode. Preferably, a portion of a bottom face of thering-shaped pad polysilicon film pattern makes contact with an upperface of the contact plug.

A method for forming an electrode of a capacitor electrode according toanother embodiment of the present invention includes forming aninsulation film including a contact plug on a semiconductor substrate,forming a conductive film on the insulation film, forming a cylindricalphotoresist pattern having an open upper face and an open bottom face onthe conductive film, the cylindrical photoresist film masking a portionof the conductive film positioned over the contact plug, and forming acylindrical conductive film pattern having an open upper face and anopen bottom face by etching the conductive film using the photoresistpattern as an etching mask until the insulation film is exposed, whereinthe cylindrical conductive film pattern makes electrical contact withthe contact plugs.

The cylindrical photoresist pattern is preferably formed by coating aphotoresist film on the conductive film, exposing the photoresist filmby irradiating a light onto a selected portion of the photoresist filmand by transmitting a portion of the light that undergoes interferenceonto a remaining portion of the photoresist film other than the selectedportion and a ring-shaped portion of the photoresist film having apredetermined width bordering the selected portion, wherein a portion ofthe conductive film corresponding to the contact plug is positionedbeneath the ring-shaped portion, and developing the exposed photoresistfilm to provide the cylindrical pattern.

The photoresist film is preferably exposed by the light irradiated ontothe selected portion and a transmitting light irradiated onto thephotoresist film other than the selected portion and the ring-shapedportion bordering the selected portion, the transmitting light having aphase that is the inverse of a phase of the light irradiated onto theselected portion.

Preferably, a first interfered light generated from a first lightirradiated onto a first selected portion is superposed with interferedlight generated from the light irradiated onto the selected portionadjacent to the first selected portion to increase an intensity of thelight exposing the photoresist film.

A width of the ring-shaped portion may be adjusted by an intensity ofthe light irradiated onto the selected portion. An exposed upper portionof the contact plug may be wider than a lower portion of the contactplug.

In accordance with another embodiment of the present invention, a methodfor forming an electrode of a capacitor includes forming a firstinsulation film including a contact plug on a semiconductor substrate,forming a first polysilicon film on the first insulation film, forming asecond insulation film on the first polysilicon film, forming acylindrical photoresist pattern having an open upper face and an openbottom face on the second insulation film by masking the secondinsulation film positioned over the contact plug, forming a cylindricalsecond insulation film pattern having an open upper face and an openbottom face by etching the second insulation film using the cylindricalphotoresist pattern as an etching mask until the first polysilicon filmis exposed, continuously forming a second polysilicon film on theexposed first polysilicon film, on a sidewall of the second insulationfilm pattern, and on the second insulation film pattern, andanisotropically etching the second polysilicon and the first polysiliconfilms so that polysilicon films partially remain only on inner and outersidewalls of the second insulation film pattern and on a bottom of thesecond insulation film pattern.

The cylindrical photoresist pattern is preferably formed by coating aphotoresist film on the second insulation film, exposing the photoresistfilm by irradiating a light onto a selected portion of the photoresistfilm and by irradiating an interfered light generated from theirradiated light onto a portion of the photoresist film other than theselected portion and a ring-shaped portion of the photoresist filmhaving a predetermined width that borders the selected portion, whereinthe second insulation film corresponding to an upper portion of thecontact plug is positioned beneath the ring-shaped portion, anddeveloping the exposed photoresist film to provide the pattern.

The photoresist film is preferably exposed by the light irradiated ontothe selected portion and a transmitting light irradiated onto theportion of the photoresist film other than the selected portion, thetransmitting light having a phase that is the inverse of a phase of thelight irradiated onto the selected portion.

Preferably, a first interfered light generated from a first lightirradiated onto a first selected portion is superposed with interferedlight generated from the light irradiated onto the selected portionadjacent to the first selected portion to increase an intensity of thelight exposing the photoresist film.

The first insulation film may be formed by successively forming an oxidefilm and a nitride film on the semiconductor substrate, forming acontact hole by successively etching portions of the nitride film andthe oxide film, filling the contact hole with a conductive material, andetching the conductive material by an etch back process until thenitride film is exposed.

Alternatively, the first insulation film may be formed by successivelyforming a first oxide film, a nitride film and a second oxide film onthe semiconductor substrate, forming a contact hole by successivelyetching portions of the first oxide film, the nitride film, and thesecond oxide film, filling the contact hole with a conductive material,and etching the conductive material by an etch back process until thesecond oxide film is exposed.

According to the present invention, when the storage node electrode ofthe capacitor is formed, an etching process may be performed using thecylindrical photoresist pattern having the open upper and bottom faces,thereby simplifying the manufacturing process of the capacitor.

BRIEF DESCRIPTION OF THE DRAWINGS

The above features and advantages of the present invention will becomemore apparent to those of ordinary skill in the art by describing indetail preferred embodiments thereof with reference to the attacheddrawings in which:

FIGS. 1A to 1D illustrate cross-sectional views depicting a conventionalmethod for forming a cylindrical capacitor;

FIG. 2 illustrates a cross-sectional view of a capacitor according to afirst embodiment of the present invention;

FIG. 3A to FIG. 3E illustrate cross-sectional views depicting a methodfor manufacturing a capacitor according to the first embodiment of thepresent invention;

FIG. 4 illustrates a schematic plan view of a phase shift mask employedfor photoresist patterns having cylindrical shapes according to a firstembodiment of the present invention;

FIG. 5 illustrates a cross-sectional view of the phase shift mask inFIG. 4;

FIG. 6 is a graph illustrating intensity profiles of lights in a casethat a phase shift mask includes one transmission region;

FIG. 7 is a graph illustrating intensity profiles of lights transmittinga phase shift mask having transmission regions regularly disposedtherein;

FIG. 8 illustrates a cross-sectional view of a capacitor according to asecond embodiment of the present invention;

FIGS. 9A to 9I illustrate cross-sectional views depicting a method formanufacturing a capacitor according to a second embodiment of thepresent invention;

FIG. 10 illustrates a schematic plane view of a phase shift maskemployed for cylindrical photoresist patterns according to a thirdembodiment of the present invention;

FIG. 11 illustrates a simulation picture of light intensity profilesobtained by employing the phase shift mask of FIG. 10;

FIG. 12 illustrates a plan picture of photoresist patterns formed byexposing a photoresist film with the phase shift mask of FIG. 10;

FIG. 13 illustrates a schematic plan view of a phase shift mask forcylindrical photoresist patterns according to a fourth embodiment of thepresent invention; and

FIG. 14 illustrates a simulation picture of light intensity profilesobtained by employing the phase shift mask of FIG. 13.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Korean Patent Application No. 2002-33027, filed on Jun. 12, 2002, andentitled: “Method For Forming A Photoresist Pattern, Method For FormingA Capacitor Using The Same And Capacitor,” is incorporated by referenceherein in its entirety.

The present invention will now be described more fully hereinafter withreference to the accompanying drawings, in which preferred embodimentsof the invention are shown. The invention may, however, be embodied indifferent forms and should not be construed as limited to theembodiments set forth herein. Rather, these embodiments are provided sothat this disclosure will be thorough and complete, and will fullyconvey the scope of the invention to those skilled in the art.

Embodiment 1

FIG. 2 illustrates a cross-sectional view of a capacitor according to afirst embodiment of the present invention.

Referring to FIG. 2, an insulation film 104 including contact plugs 102is formed on a semiconductor substrate 100. The contact plugs 102 areelectrically connected to a capacitor node contact region (for example,a source region of a transistor) of the semiconductor substrate 100where an active region is defined. The contact plugs 102 are formedthrough the insulation film 104 formed on the substrate 100. At thistime, the contact plugs 102 are regularly positioned on the substrate100.

Storage node electrodes 106 a having a cylindrical shape are formed onthe insulation film 104. The storage node electrodes 106 a areelectrically connected to the contact plugs 102. Bottom faces of thestorage node electrodes 106 a are open. A portion of the bottom face ofeach of the storage node electrodes 106 a makes contact with an upperface of each of the contact plugs 102.

A dielectric film 110 and a plate electrode 112 are sequentially formedon the storage node electrodes 106 a. Hereinafter, a method formanufacturing the above-mentioned capacitor will be described.

FIG. 3A to FIG. 3E illustrate cross-sectional views depicting a methodfor manufacturing a capacitor according to the present embodiment.

FIG. 3A shows a step for forming an insulation film 104 includingcontact plugs 102 on a semiconductor substrate 100.

Referring to FIG. 3A, each of the contact plugs 102 makes electricalcontact with a capacitor node contact region of the semiconductorsubstrate 100. The contact plugs 102 are regularly disposed on thesemiconductor substrate 100.

The step for forming the insulation film 104 including the contact plugs102 will be described as follows.

A field region and an active region are defined in the semiconductorsubstrate 100 by an isolation process. A semiconductor device may bepositioned in the active region of the semiconductor substrate 100.

A device structure (not shown) including a capacitor node contact regionis formed in the active region of the substrate 100. The devicestructure may include a metal oxide semiconductor (MOS) transistor and abit line. Particularly, after a gate oxide film having a thin thicknessis formed in the active region of the semiconductor substrate 100, agate electrode having a polycide structure is formed on the gate oxidefilm. The gate electrodes may include a polysilicon film doped withimpurities, and a tungsten silicide film. Then, source/drain regions ofa transistor are formed at surface portions of the semiconductorsubstrate 100 by implanting impurities onto the substrate 100 using thegate electrode as a mask.

An interlayer dielectric film is formed on the semiconductor substrate100 where the transistor is formed, and a bit line contact hole isformed by etching a predetermined portion of the interlayer dielectricfilm. A polysilicon film doped with impurities is formed to fill up thebit line contact hole, and a tungsten silicide film is formed on thepolysilicon film. The polysilicon and tungsten silicide films arepatterned using a photolithography process to provide a bit line havinga polycide structure. The bit line may make contact with the sourceregion of the transistor or a drain region of the transistor.

An insulation film is additionally formed on the semiconductor substrate100 where the device structure is positioned. A predetermined portion ofthe insulation film is etched to form a contact hole that exposes thesource region of the semiconductor substrate 100. At this time, thecontact hole may have an upper portion wider than a bottom face thereofby etching the contact hole with a predetermined inclination. Aconductive material fills the contact hole, and the insulation film isplanarized by an etch back process to provide the insulation film 104including the contact plugs 102.

Referring to FIG. 3B, a polysilicon film 106 doped with impurities isformed on the insulation film 104 including the contact plugs 102.Because storage node electrodes are successively formed through thepolysilicon film 106, the polysilicon film 106 is formed to have apredetermined height higher than heights of the storage node electrodes.Recently, a height of a storage node electrode has been increased toimprove a storage capacitance of a capacitor. The storage node electrodegenerally has a height of about 7,000 to about 18,000 Å.

Referring to FIG. 3C, a mask (not shown) is disposed over a portion ofthe polysilicon film 106 under which the contact plugs 102 arepositioned. Cylindrical photoresist patterns 108 are formed on thepolysilicon film 106. In this case, both upper and lower faces of thephotoresist patterns 108 are open.

Particularly, a photoresist film is coated on the polysilicon film 106.At this time, a thickness of the photoresist film may be determined byconsidering an etching selectivity of the photoresist film relative tothe underlying polysilicon film 106. Namely, the photoresist film mayhave a sufficient thickness so that the photoresist film is not entirelyconsumed during a successive etching process in which the polysiliconfilm patterns are completely formed. For example, in a case that thepolysilicon film 106 is about 7,000 Å thick, and an etching selectivitybetween the polysilicon film 106 and the photoresist film is about 2:1,the photoresist film preferably has a thickness of more than about 3,500Å.

A phase shift mask is disposed over the photoresist film. The phaseshift mask includes transmission regions regularly disposed therein anda blocking (partially blocking or partially transmitting) regionenclosing the transmission regions. The transmission regions transmit afirst light, and the blocking region transmits a second light having aphase angle that is the inverse of a phase angle of the first light.That is, the phase angle of the second light transmitted through theblocking region is shifted by 180° with respect to the phase angle ofthe first light. At this time, an intensity of the second lighttransmitted through the blocking region may be about 5 to about 50% ofan intensity of the first light transmitted through the transmissionregions.

FIGS. 4 and 5 illustrate a plan view and a cross-sectional view,respectively, of the phase shift mask employed for the photoresistpatterns having the cylindrical shapes.

Referring to FIGS. 4 and 5, a phase shift mask 150 has a lower film 152and an upper film 154 positioned on the lower film 152. The lower film152 preferably includes quartz and the upper film 154 preferablyincludes a phase shifting material, such as MoSiON. Portions of theupper film 154 corresponding to transmission regions A are etched topartially expose the lower film 152. The transmission regions A have arectangular shape, and correspond to insides of the cylindricalphotoresist patterns, respectively.

A light is irradiated onto the photoresist film while the phase shiftmask 150 is disposed over the photoresist film.

FIG. 6 is a graph illustrating intensity profiles of the light in a casethat the phase shift mask 150 includes one transmission region Isurrounded by a blocking region having a first portion II and a secondportion III.

Referring to FIG. 6, the light intensity of the transmission region I ofthe phase shift mask 150 is a higher than a light intensity of any otherregion of the phase shift mask 150. Light beams having different phasesinterfere destructively with each other in the first portion of theblocking region II, which is adjacent to a peripheral portion of thetransmission region I, because phase inversion of the light beams mayoccur between the transmission region I and the first portion of theblocking region II. Thus, the first portion of the blocking region IImay have the lowest light intensity.

Meanwhile, a second portion of the blocking region III, which is nearthe first portion of the blocking region II adjacent to a peripheralportion of the transmission region I, may have a higher light intensitysince an interfered light and a diffracted light of the light irradiatedto transmission region I are permeated through the second portion of theblocking region II. As the intensity of the light transmitted throughthe second portion of the blocking region III becomes higher, parasitepatterns may be formed causing a processing failure.

FIG. 7 is a graph illustrating an intensity profile of light passingthrough a phase shift mask having transmission regions C₁ regularlydisposed therein, surrounded by a blocking region having a first portionC₂ and a second portion C₃.

As shown in FIG. 7, when the transmission regions C₁ are arranged in thephase shift mask by a regular interval, interfered light and diffractedlight of the light irradiated to the transmission regions C₁ aresuperposed at the second portion of the blocking region C₃ to causeconstructive interference. Hence, the light intensity transmitted fromthe first portions of the blocking region C₂ to the second portion C₃,where the constructive interference occurs, may be increased to providesufficient light for exposing the photoresist film.

Referring to FIG. 4 again, the phase shift mask 150 includes therectangular shaped transmission regions A regularly disposed therein,surrounded by a blocking region including a first portion B₁ borderingthe transmission regions A and a second portion B₂.

When an exposure process is performed using the phase shift mask 150, anintensity of light has a minimum value at the first portion of theblocking region B₁ adjacent to peripheral portions of the transmissionregions A. The first portion of the blocking region B₁ may have apredetermined width along a boundary between the second portion of theblocking region B₂ and the transmission region A. Because thetransmission regions A have a rectangular shape, the first portion ofthe blocking region B₁ having a lower light intensity has a ring shape.Light beams are sufficiently provided onto the regions A and B₂ toexpose the photoresist film except for the ring shaped portion of theblocking region B₁. A width of the first portion of the blocking regionB₁ having the ring shape may be desirably adjusted by controlling theintensity of light irradiated onto the phase shift mask 150. As aresult, a width of the photoresist pattern may be adjusted, and thephotoresist pattern may have a width of below about 100 nm (preferably10 to 100 nm, more preferably 50 to 100 nm).

The first portion of the blocking region B₁ having the ring shape islocated to mask the portions of the polysilicon film 106 positioned overthe contact plugs 102. The transmission regions A of the phase shiftmask 150 are not positioned directly over the underlying contact plugs102, and a bottom face of the transmission regions A is adjacent to anupper face of each of the contact plugs 102.

Referring now to FIG. 3D, storage nodes 106 a of a capacitor are formedby etching the polysilicon film 106 of FIG. 3C using the cylindricalphotoresist patterns 108 as etching masks until the insulation film 104is exposed. With the etching process, the polysilicon film 106 isconverted into polysilicon patterns 106 a making contact with theunderlying contact plugs 102. The polysilicon patterns 106 a have openupper and lower faces, respectively. In addition, a portion of each ofthe polysilicon patterns 106 a makes contact with each of the underlyingcontact plugs 102, respectively.

According to the method described above for manufacturing the capacitor,storage nodes can be formed by one etching process. Therefore, processesfor separating storage nodes, depositing a sacrificial layer,planarizing the sacrificial layer, and removing an insulation film, forexample, may be omitted in comparison with the conventional method forforming a capacitor.

Referring FIG. 3E, a dielectric film 110 and a conductive film 112 for aplate electrode are successively formed on the storage nodes 106 a,thereby completing the capacitor.

Embodiment 2

FIG. 8 illustrates a cross-sectional view of a capacitor according to asecond embodiment of the present invention.

Referring to FIG. 8, an insulation film 204 including contact plugs 202is formed on a semiconductor substrate 200. The insulation film 204 mayinclude a composite film having an oxide film 204 a and an etch stopfilm 204 b sequentially formed on the oxide film 204 a. The contactplugs 202 are regularly disposed on the semiconductor substrate 200.

Particularly, the insulation film 204 includes the contact plugs 202electrically connected to a node contact region, for example, a sourceregion of a transistor, of the semiconductor substrate 200 in which anactive region is defined.

Ring-shaped pad polysilicon film patterns 206 a electrically connectedto the contact plugs 202 are formed on the contact plugs 202. A portionof each of the bottom faces of the ring-shaped pad polysilicon filmpatterns 206 a makes contact with an upper portion of each of thecontact plugs 202.

Spacer-shaped patterns 212 a are formed on the ring-shaped patterns 206a. The spacer shaped patterns 212 a make continuous contact with insidesand outsides (inner and outer upper peripheral portions) of thering-shaped patterns 206 a. The spacer shaped patterns 212 a are formedto extend vertically from the insides and outsides of the ring-shapedpatterns 206 a, thereby providing double cylindrical storage nodeelectrodes 213.

A dielectric film 214 and plate electrodes 216 are sequentially formedon the storage node electrodes 213, respectively.

A method for manufacturing the capacitor having the above-describedconstruction will be described as follows.

FIGS. 9A to 9I illustrate cross-sectional views depicting a method formanufacturing a capacitor according to the present embodiment.

Referring to FIG. 9A, a first insulation film 204 including contactplugs 202 is formed on a semiconductor substrate 200. The contact plugs202 are electrically connected to a capacitor node contact region of thesemiconductor substrate 200. The first insulation film 204 may include acomposite film having an oxide film 204 a and an etch stop film 204 b.Although it is not shown in the figures, the first insulation film 204may include a composite film having an oxide film, an etch stop film andan additional oxide film. When an additional oxide film having a thinthickness is formed on the etch stop film, consumption of the etch stopfilm or generation of particles may be prevented during a successiveetching process.

Hereinafter, the processes described above will be explained in detail.

The oxide film 204 a and the etch stop film 204 b are sequentiallyformed on the semiconductor substrate 200 where a device structure (notshown) is formed. Preferably, the etch stop film 204 b includes siliconnitride that has a high etching selectivity relative to the oxide film204 a.

Predetermined portions of the etch stop and oxide films 204 b and 204 aare successively etched to provide contact holes exposing node contactregions of the semiconductor substrate 200, for example, source regionsof a transistor. The contact holes are regularly formed on thesemiconductor substrate 200.

In the etching process, upper portions of the contact holes may be widerthan bottom portions of the contact holes by etching the etch stop andoxide films 204 b and 204 a with a predetermined inclination.

A conductive material is deposited to fill the contact holes, and anupper portion of the etch stop film 204 b is planarized, thereby formingthe first insulation film 204 including the contact plugs 202. Thecontact plugs 202 are regularly formed through the first insulation film204.

Referring to FIG. 9B, a first polysilicon film 206 doped with impuritiesis formed on the first insulation film 204 including the contact plugs202. Later, the first polysilicon film 206 will serve as bottom faceportions of storage node electrodes that are electrically connected tothe contact plugs 202.

Referring to FIG. 9C, a second insulation film 208 is formed on thefirst polysilicon film 206. In this case, a height of the secondinsulation film 208 is higher than those of the storage node electrodes.Generally, heights of the storage node electrodes have been increased toincrease a storage capacitance of a capacitor so that the storageelectrode may have a height of about 7,000 to about 18,000 Å.

Referring to FIG. 9D, cylindrical photoresist patterns 210 are formed onthe second insulation film 208 while portions of the second insulationfilm 208 over the contact plugs 202 are masked. Upper and bottom facesof the photoresist patterns 210 are open, and the photoresist patterns210 have a width of d.

In the formation of the photoresist patterns, a photoresist film iscoated on the second insulation film 208. A thickness of the photoresistfilm is determined in accordance with an etching selectivity between thephotoresist film and the underlying second insulation film 208. Namely,the photoresist film is formed to have a sufficient thickness so thatthe photoresist patterns may not be entirely consumed until secondinsulation film patterns are completely formed during a successiveetching process. For example, when a thickness of the second insulationfilm 208 is about 7,000 Å and an etching selectivity between the secondinsulation film 208 and the photoresist film is about 2:1, thephotoresist film has a thickness of more than about 3,500 Å.

A phase shift mask identical to that of FIG. 4 is positioned over thephotoresist film. The phase shift mask includes transmission regionsregularly disposed therein and a blocking (partially blocking orpartially transmitting) region enclosing the transmission regions. Thetransmission regions transmit a first light, and the blocking regiontransmits a second light having a phase angle inverted by about 180°concerning that of the first light. In this case, an intensity of thesecond light transmitted through the blocking region may be about 5 toabout 50% of an intensity of the first light transmitted through thetransmission regions.

Rectangular shaped transmission regions are regularly arranged in thephase shift mask. When a light is irradiated onto the phase shift mask,an intensity of the light is at a minimum at a portion of the blockingregion located at a boundary between the transmission regions and theblocking region. The portion of the blocking region at the boundary ofthe transmission regions has a predetermined width and surrounds thetransmission regions. The light intensity is at a minimum in theboundary region because light that is transmitted through the blockingregion interferes destructively with the light that is transmittedthrough the transmission regions at the boundary region. This is becausethe light transmitted through the blocking region is inverted withrespect to the light transmitted through the transmission regions,causing the light to “cancel.” In the meantime, portions of the blockingregion other than the portion at the boundary between the transmissionand the blocking regions may have a slightly increased light intensitybecause interfered light and diffracted light of the light that isirradiated to the transmission regions are transmitted to the blockingregion where they interfere constructively.

Since the transmission regions are regularly disposed in the phase shiftmask, superposition between the interfered light and the diffractedlight occurs to cause constructive interference at portions of theblocking region other than the boundary between the blocking region andthe transmission regions. Therefore, light sufficient to expose thephotoresist film may be provided at a portion of the blocking regionwhere the constructive interference occurs, since the light intensity isincreased in that region. As a result, solubility of the photoresistfilm varies at different portions of the blocking region. Meanwhile, theboundary portion of the blocking region having the minimum lightintensity may have a ring shape since the transmission regions have arectangular shape.

The ring shaped portions of the blocking region having the lowest lightintensity are disposed over the second insulation film 208 to maskportions of the second insulation film 208 positioned over the contactplugs 202. The transmission regions of the phase shift mask are notpositioned directly over the contact plugs 202 while bottom faceportions of the transmission regions may be adjacent to the contactplugs 202. A width of the ring shaped portions of the blocking regionshaving the lowest light intensity may be adjusted by controlling theintensity of the light irradiated onto the phase shift mask, therebyadjusting the width of the photoresist pattern.

With an exposure process according to the above-described principle, acylindrical photoresist pattern 210 is formed on the second insulationfilm 208 after a developing process is performed.

Referring to FIG. 9E, a cylindrical second insulation film pattern 208 ais formed on the first polysilicon film 206 by etching the secondinsulation film 208 using the cylindrical photoresist pattern 210 as anetching mask until the first polysilicon film 206 is exposed. The secondinsulation film patterns 208 a have open bottom faces, respectively. Atthis time, a portion of each of the bottom faces of the secondinsulation film patterns 208 a is formed on the first polysilicon film206 positioned over each of the contact plugs 202.

Referring to FIG. 9F, a second polysilicon film 212 is continuouslyformed on an exposed portion of the first polysilicon film 206, onsidewalls of the second insulation film patterns 208 a, and on upperfaces of the second insulation film patterns 208 a. The secondpolysilicon film 212 has a thickness of about 500 to about 2,000 Å.

Referring to FIG. 9G, the second and first polysilicon films 212 and 206are anisotropically etched so that portions 212 a and 206 a,respectively, of the second and first polysilicon films 212 and 206remain at insides and outside the second insulation film patterns 208 a,and beneath bottom faces of the second insulation film patterns 208 a.When an anisotropic etching process is performed for the second andfirst polysilicon films 212 and 206, the first polysilicon film 206 isconverted into a ring-shaped pattern 206 a while the second polysiliconfilm 212 is changed into patterns 212 a having shapes similar tosidewall spacers of the second insulation film patterns 208 a. To forman isolated ring-shaped first polysilicon film pattern 206 a without aconnection between the adjacent ring-shaped patterns 206 a, the secondand first polysilicon films 212 and 206 are preferably over-etched.

Referring to FIG. 9H, double cylindrical storage node electrodes 213 areformed by removing the remaining second insulation film patterns 208 a.

Particularly, the second insulation film patterns 208 a areanisotropically etched by immersing the resultant structure formedthrough the steps described in FIG. 9A and FIG. 9B in an etchingsolution. Because the etch stop film 204 b is formed on the oxide film204 a, the oxide film 204 a is not etched during etching the secondinsulation film patterns 208 a. Thus, the double cylindrical storagenode electrodes 213 can include the spacer-shaped patterns 212 a thatmake continuous contact with insides and outsides (inner and outer upperperipheral portions) of the ring-shaped patterns 206 a while thespacer-shaped patterns 212 a extend vertically from the insides andoutsides of the ring-shaped patterns 206 a to provide the doublecylindrical storage node electrodes 213.

Referring to FIG. 9I, a capacitor is completed by successively formingdielectric films 214 and conductive films 216 for plate electrodes onthe storage node electrodes 213, respectively.

Embodiment 3

FIG. 10 illustrates a schematic plan view of a phase shift mask forcylindrical photoresist patterns according to a third embodiment of thepresent invention.

Referring FIG. 10, the phase shift mask includes first transmissionregions 300 a positioned along odd vertical lines and secondtransmission regions 300 b disposed along even vertical lines. Positionsof the first transmission regions 300 a on a conventional X-axis of thephase shift mask are different from those of the second transmissionregions 300. The first and second transmission regions 300 a and 300 bhave rectangular shapes that have widths L₁ of about 250 nm and heightsL₂ of about 200 nm. A first side of a transmission region is a distanceL₃ from a first side of an adjacent transmission region in theX-direction and a first side of a transmission region is a distance L₄from a first side of an adjacent transmission region in a conventionalY-direction. Distance L₃ is about 500 nm and distance L₄ is about 400nm.

FIG. 11 illustrates a simulation picture of a light intensity profileobtained by employing the phase shift mask in FIG. 10.

In FIG. 11, conditions of a simulation for the light intensity profilesare as follows:

a transmission rate in an inversion region (boundary region) of thephase shift mask of about 20%;

an optical system having an NA of about 0.6, a σ of about 0.4, and aconventional diameter, where σ and NA equal, respectively, the partialcoherence and numerical aperture of the exposure tool.; and

an exposure amount of about 65mJ/cm²sec.

In this case, an intensity of light shows the lowest value at a portionof a blocking region 310 adjacent to a boundary between the transmissionregion and the blocking region because light having different phasesinterferes destructively at the boundary. Portions of the blockingregion 310 other than that at the boundary of the transmission andblocking regions, have a light intensity similar to that of thetransmission regions 300 a and 300 b. This is because diffracted lightof the light irradiated to the transmission regions 300 a and 300 binterferes with light transmitted through other portions of the blockingregion. Therefore, cylindrical photoresist patterns may be formed usingthe phase shift mask under the above-mentioned conditions.

FIG. 12 illustrates a plan view of photoresist patterns formed byexposing a photoresist film with the phase shift mask of FIG. 10.

The photoresist patterns in FIG. 12 are formed as follows.

An oxide film having a thickness of about 1,000 Å and a nitride filmhaving a thickness of about 300 Å are formed on a substrate. The nitridefilm functions as an anti-reflection layer. A photoresist film having athickness of about 7,000 Å is formed on the nitride film. Thephotoresist film is exposed using the phase shift mask as shown in FIG.10.

Exposure conditions of an exposure process for the photoresist film areas follows:

a transmission rate in an inversion region of the phase shift mask isabout 20%;

an optical system having an NA of about 0.6, a σ of about 0.4, aconventional diameter; and

an exposure amount of about 65mJ/cm²sec.

With the above-mentioned exposure conditions, the photoresist patternsmay have a cylindrical shape. The cylindrical photoresist patterns havea ring shape. In addition, widths R₁ of the ring-shaped photoresistpatterns are about 70 nm, and inner diameters R₂ of inner circle ofcylindrical photoresist patterns are about 220 nm.

Embodiment 4

FIG. 13 illustrates a schematic plan view of a phase shift mask forcylindrical photoresist patterns according to a fourth embodiment of thepresent invention.

Ah shown in FIG. 13, a phase shift mask includes first transmissionregions disposed along odd lines and second transmission regionspositioned along even lines. The positions of the first transmissionregions on an X-axis of the phase shift mask are identical to those ofthe second transmission regions on the X-axis. The transmission regionshave a rectangular shape in which widths D₁ of the transmission regionsare about 180 nm and heights D₂ of the transmission regions are about180 nm. As for the transmission regions, intervals D₃ between adjacenttransmission regions along the X-axis are about 450 nm, and intervals D₄between adjacent transmission regions along a Y-axis of the phase shiftmask are about 450 nm centering about central points of the transmissionregions adjacent to each other.

FIG. 14 illustrates a simulation picture of light intensity profilesobtained by employing the phase shift mask as shown in FIG. 13.

In FIG. 14, conditions of a simulation for the light intensity profilesare as follows:

a transmission rate in an inversion region of the phase shift mask ofabout 20%;

an optical system having an NA of about=0.8, a σ of about 0.3, and aconventional diameter; and

an exposure amount of about 65mJ/cm²sec.

In this case, light intensity is at a minimum at a boundary portion of ablocking region 330 of the phase shift mask adjacent to a boundarybetween the transmission region and the blocking region 330 becauselight having different phases interfere destructively with each other inthat region. Portions of the blocking region 330 other than the portionat the boundary between the blocking region and the transmission regionshave a light intensity that is similar to the light intensity of thetransmission regions. This is because diffracted light of light that isirradiated onto the transmission regions interferes with the lights thatare transmitted through the other portions of the blocking region 330.Therefore, since the transmission regions have a rectangular shape,cylindrical photoresist patterns may be formed by employing the phaseshift mask under the above-mentioned conditions.

As described above, according to the present invention, manufacturingprocesses for a semiconductor device may be simplified by employingphotoresist patterns having cylindrical shapes.

Preferred embodiments of the present invention have been disclosedherein and, although specific terms are employed, they are used and areto be interpreted in a generic and descriptive sense only and not forpurpose of limitation. Accordingly, it will be understood by those ofordinary skill in the art that various changes in form and details maybe made without departing from the spirit and scope of the invention asset forth in the following claims.

1. A capacitor of a semiconductor device comprising: an insulation filmincluding a contact plug on a semiconductor substrate; a cylindricalstorage node electrode formed on the insulation film, wherein thestorage node electrode makes electrical contact with the contact plugand has an open bottom face; and a dielectric film and a plate electrodeon the storage node electrode.
 2. The capacitor as claimed in claim 1,wherein a portion of the bottom face of the storage node electrode makescontact with an upper face of the contact plug.
 3. The capacitor asclaimed in claim 1, wherein the capacitor includes a plurality ofcontact plugs and a corresponding plurality of storage node electrodes.4. The capacitor as claimed in claim 3, wherein the plurality of contactplugs are arranged at regular intervals.
 5. The capacitor as claimed inclaim 1, further comprising a ring shaped pad electrically connected tothe contact plug.
 6. The capacitor as claimed in claim 5, wherein thecylindrical storage node electrode is a double cylindrical storage nodeelectrode in electrical contact with the ring-shaped pad, wherein thestorage node electrode extends vertically from surfaces of thering-shaped pad.
 7. The capacitor as claimed in claim 1, wherein thecontact plug is electrically connected to a capacitor node contactregion.
 8. A capacitor of a semiconductor device comprising: aninsulation film including a contact plug on a semiconductor substrate; aring-shaped pad electrically connected to the contact plug; a doublecylindrical storage node electrode in electrical contact with thering-shaped pad, wherein the storage node electrode extends verticallyfrom surfaces of the ring-shaped pad; and a dielectric film and a plateelectrode on the storage node electrode.
 9. The capacitor as claimed inclaim 8, wherein a portion of a bottom face of the ring-shaped pad makescontact with an upper face of the contact plug.
 10. The capacitor asclaimed in claim 8, wherein the storage node electrode extendsvertically from inner and outer surfaces of the ring shaped pad.
 11. Thecapacitor as claimed in claim 10, wherein the storage node electrode isin continuous contact with the inner and outer surfaces of the ringshaped pad.
 12. The capacitor as claimed in claim 8, wherein thering-shaped pad is a polysilicon film.
 13. The capacitor as claimed inclaim 8, wherein the capacitor includes a plurality of contact plugs anda corresponding plurality of storage node electrodes.
 14. The capacitoras claimed in claim 13, wherein the plurality of contact plugs arearranged at regular intervals.
 15. The capacitor as claimed in claim 8,wherein the contact plug is electrically connected to a capacitor nodecontact region.
 16. The capacitor as claimed in claim 8, wherein theinsulation film includes an oxide film and an etch stop film on theoxide film.